This class is basically used to add special style to the element that is the first child of another element.

<html><head><style type="text/css">div>p:first-child{text-indent:25px;color:#FF00FF;}</style></head><body><div><p>Here INCLUDEHELP is intendent</p><p>Here INCLUDEHELP is not indented</p></div><p>But this will not change the paragraph in HTML document:
</p><div><p>Here INCLUDEHELP will not be effected.</p></div></body>